1. Field of the Invention
The invention relates to a six-coordinated ruthenium complex which is suitable for use as a dye in a dye-sensitized solar cell, more particularly to a six-coordinated ruthenium complex which includes a 1-(haloalkylpyrazole)-isoquinoline-based bidentate ligand.
2. Description of the Related Art
In recent years, solar cells have been developed with the increasing demand for energy. In particular, the dye-sensitized solar cells have shown most promise among solar cells. The dye-sensitized solar cells absorb visible light and near infrared light to excite electrons. The excited electrons are effectively transferred to a conduction band of a semiconductor electrode in the dye-sensitized solar cells to generate a photocurrent. Therefore, the property of a dye used in the dye-sensitized solar cells would affect directly the photoelectric conversion efficiency of the dye-sensitized solar cell. At present, the ruthenium complex is the main target of research for the dye in the solar cell.
US Patent Application Publication No. 2011/0277841 A1 discloses a photosensitizer represented by the following formula (a):RuXYZ  (a)
wherein Ru is ruthenium; X, Y, and Z independently represent a bidentate heterocyclic ligand; X has a structure represented by the following formula (b); Y has a structure represented by the following formula (b), (c), (d), or (e); and Z has a structure represented by the following formula (c), (d), or (e).




In the formulas (a), (b), (c), and (d), Ra, Rb, Rc, Rd, Re, Rf, Rg, Rh, Ri, Rj, Rk, Rl, Rm, Rn, Ro, Rp, Rq, and Rr are independently selected from the group consisting of hydrogen, halogen, an aryl group, an alkenyl group, a C1-C20 alkyl group, a cycloalkyl group, an alkynyl group, CN, CF3, an alkylamino group, an amino group, an alkoxy group, a heteroaryl group, a halogen substituted aryl group, a haloalkyl substituted aryl group, a haloalkyl substituted aromatic group, and an aryl substituted C1-C20 alkyl group.
In the aforesaid publication, a photosensitizer represented by the following formula (o) is disclosed:

When the photosensitizer of formula (o) is used in the dye-sensitized solar cell, the dye-sensitized solar cell has 12.7 mAcm−2 of short circuit current density and 7.84% of photoelectric conversion efficiency. However, the photoelectric conversion efficiency of the conventional dye-sensitized solar cell still cannot satisfy the demand in the industry.